Design Considerations for Toxic Chemical and ... - ACS Publications

Chapter 20

Design and Use of Ammunition Peculiar Equipment To Protect Workers Mark M. Zaugg

Downloaded by RUTGERS UNIV on May 14, 2018 | https://pubs.acs.org Publication Date: July 20, 1987 | doi: 10.1021/bk-1987-0345.ch020

Tooele Army Depot, Tooele, UT 84074

Discusses the use of Ammunition Peculiar Equipment (APE) used by the military community to perform various operations on ammunition items. Ways in which operators are protected when using APE are included. Specifically, the design of operational shields to contain effects of an explosion is explained. Ammunition Peculiar Equipment, commonly referred to as APE, i s specialized equipment f o r use i n the maintenance, modification, renovation, surveillance and d e m i l i t a r i z a t i o n of ammunition items. This equipment i s used a t world wide m i l i t a r y i n s t a l l a t i o n s with ammunition missions that require any of the above mentioned activities. Whenever the operation to be performed involves the p o t e n t i a l to cause the i n i t i a t i o n of the propellant, explosive or pyrotechnic (PEP) component(s) of a munition item, the APE i s either operated by remote c o n t r o l , with the operator behind a protection w a l l or b a r r i e r , or i t i s enclosed i n a protective barricade or operational s h i e l d . Barricades or operational shields are designed to protect personnel and assets from the effects of b l a s t overpressures, thermal effects or f i r e b a l l , and fragments r e s u l t from the i n i t i a t i o n of PEP components, such as the fuze, primer, p r o p e l l i n g charge, burster, e t c . Operational shields are designed and tested i n accordance with MIL-STD 398, Shields, Operational f o r Ammunition Operations, C r i t e r i a f o r Design of and Tests for Acceptance, dated 5 November 1976 (see reference 1). This m i l i t a r y standard provides c r i t e r i a for the protection of personnel and assets from the effects of accidental or i n t e n t i o n a l detonation and deflagrations, considering the maximum c r e d i b l e incident (MCI) involving the maximum amount of ammunition and explosives within or adjacent to an operational s h i e l d , that w i l l detonate or deflagrate as a r e s u l t of the functioning of a single item.

This chapter not subject to U.S. copyright Published 1987 American Chemical Society

Scott and Doemeny; Design Considerations for Toxic Chemical and Explosives Facilities ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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Operational shields are to be designed to conform to the following requirements: BLAST ATTENTION. Shields used to provide protection from accidental detonation, are to be designed to prevent exposure of operating personnel to peak p o s i t i v e incident pressures above 2.3 psi or peak p o s i t i v e normal r e f l e c t e d pressure above 5.0 p s i .


Shields used to provide protection from i n t e n t i o n a l detonation of ammunition are to be designed to prevent exposure of operating personnel to impulse noise l e v e l s exceeding 140 decibels. FRAGMENT CONFINEMENT. Shields are to be designed to contain a l l fragmentation, or d i r e c t fragmentation away from areas requiring protection. They are also to prevent generation of secondary fragmentation within areas requiring protection, and prevent movement, overturning, or s t r u c t u r a l deflections which could r e s u l t i n personnel injury. THERMAL EFFECTS ATTENUATION. Shield designs are to also l i m i t exposure of personnel to a c r i t i c a l heat f l u x value based on the t o t a l time of exposure. This value of heat f l u x i s determined by the following equation: 7423

9 = 0.62t-°' where: 0 = heat f l u x i n cal/cm2-sec t = t o t a l time i n seconds that a person i s exposed to the radiant heat Operating personnel are to be located a t a distance from the s h i e l d that assures their exposure i s less than the heat f l u x determined by the above equation. In a d d i t i o n , the upper torso of an operator's body s h a l l not be subjected to any v i s i b l e f i r e or flame. Flame impingement upon the lower portion of the body may be permitted provided that the heat f l u x specified above i s not exceeded. ASSET PROTECTION. Shields intended f o r i n t e n t i o n a l detonation are to be designed to prevent damage to buildings, equipment, and other assets i n the area. Damage prevention i s considered adequate i f normal operations are i n no way interrupted or hindered as a r e s u l t of any change to the operational environment from explosions i n this type of s h i e l d , and the s h i e l d may be expected to remain operational throughout i t s designed l i f e cycle. Shields designed f o r accidental explosions only are designed to provide personnel protection from the MCI at that operation and may not, i n a l l cases provide asset protection. SHIELD DESIGN. In the i n i t i a l approach to operational s h i e l d design, the hydrostatic pressure that would r e s u l t from the MCI in the s h i e l d i s determined. For a high explosive detonated i n a


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closed a i r space, a hydrostatic pressure develops w i t h i n the space subsequent to the shock wave propagation. This pressure can be found from the equation: ΔΡ - 4000 hw/v where: h = heat of combustion (kcal/gm) (Table I) w = charge weight ( l b ) ν =• volume of a i r ( f t 3 ) Po = S t a t i c pressure above ambient ( p s i )


β

This equation i s derived from the energy equation of state for gas Ε = P V ( f - l ) , which b a s i c a l l y gives the hydrostatic pressure produced by the burning of a substance i n a f i x e d volume of a i r without a heat l o s s , (see reference 2). I t should be noted that the above r e l a t i o n s h i p applies to bare explosive charges. S t a t i c pressure from cased charges w i l l be smaller than those predicted by the equation because of k i n e t i c energy acquired by case fragments. The s t a t i c pressure decays with time as a function of the heat conduction and convection v a r i a b l e s of the s h i e l d , and the degree of pressure venting provided. Table I. Heats of Combustion f o r Several Explosives are Contained

Explosives PETN RDX P e n t o l i t e 50/50 Comp Β Tetryl TNT HBX-1 H-6 T r i t o n a l 80/20 HBX-3

Heat of Combustion kcal/gm 1.95 2.28 2.79 2.82 2.93 3.62 3.73 3.84 4.38 4.56

Once the s t a t i c pressure has been determined, the i n i t i a l s h i e l d design can be done using standard unfired pressure vessel design methods. The geometric shape of the s h i e l d i s of course driven by the shape of the machine to be contained and the a v a i l a b l e space i n the operating area where the machine and operational s h i e l d are to be located. Once the i n i t i a l design has been made, the dynamic response of the designed s h i e l d members to the dynamic pressure i s checked. This i s necessary to ensure that deflections of s t r u c t u r a l members due to loading from dynamic pressure produced by the MCI, namely the peak p o s i t i v e incident and r e f l e c t e d pressures, does not permit the escape of fragments or heat f l u x that would endanger personnel.


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Unless s p e c i f i c a l l y designed to do so, operational shields do not t o t a l l y contain and hold the pressures generated from an explosion. Venting of pressures occurs through j o i n t s , flanges, and openings i n the s h i e l d , and may be enhanced by providing large vented openings that exhaust through the roof or w a l l of the b u i l d i n g i n which the s h i e l d i s located.


The next f a c t o r i n the s h i e l d design i s to design for prevention of fragment penetration of the s h i e l d material. Fragment penetration can not only be a d i r e c t hazard to operating personnel, but p a r t i a l penetration can weaken the s h i e l d causing subsequent f a i l u r e from the overpressures. Fragment data and c r i t e r i a for s h i e l d design to prevent penetration are contained i n chapter 2 of reference 3 and i n reference 4. Knowing that the pressure and f i r e b a l l w i t h i n the s h i e l d from an MCI w i l l be vented through flanges, openings and j o i n t s , the design should provide for long, close tolerance, and i f possible, c i r c u i t o u s routes for the pressure and f i r e b a l l to t r a v e l . This w i l l help eliminate passage of fragments outside the s h i e l d through openings caused by deflections of s h i e l d members. I t also provides for quenching of the f i r e b a l l by heat transfer from the hot gases to the passageway. SHIELD TESTING. After the design of the s h i e l d has s a t i s f i e d the requirements, and the prototype s h i e l d has been fabricated, reference 1 s p e c i f i e s the t e s t i n g to which i t must be subjected. The prototype operational s h i e l d must be tested by creating an MCI i n a simulated operational environment. The MCI i s created by detonating or i g n i t i n g a t e s t round(s), or item(s) with a l l items i n the operational configuration i n the s h i e l d , including the equipment or reasonable simulation thereof, that performs the intended function on the munitions. I f the s h i e l d i s intended to be used for a v a r i e t y of rounds, the one(s) having the most severe e f f e c t s for overpressure, fragmentation, thermal emissions and shape charge e f f e c t s i s to be tested. For each test the s h i e l d must be repaired to the equivalent of new condition or a new s h i e l d used, except f o r shields intended for i n t e n t i o n a l detonations. A d d i t i o n a l explosives equivalent to 25 percent of the explosive f i l l e r i s added to the test round, i f i t can be applied i n a manner as not to diminish the normal e f f e c t and response of the ammunition. The t e s t should also be conducted i n a l o c a t i o n that simulates the l o c a t i o n when i t w i l l be s p e c i f i c a l l y used. For example, shields to be used i n an operational bay should be tested i n a simulation of an operational bay.


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Table I I . L i s t of Instrumentation 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

1 1 4 4 1 1 1 7 1 1

ea ea ea ea ea ea ea ea ea ea

11. 12. 13. 14. 15. 16.

1 1 1 1 1 1

ea ea ea ea ea ea

1. 1 ea 2. 1 ea 3. 1 ea 4. 1 ea 5. 1 ea 6. 1 ea 7. 2 ea 8. 1 ea 9. 1 ea 10. 1 ea 11. 1 ea

Honeywell 7610 Instrumentation Tape Recorder A r t i s a n EPC 19061 D i g i t a l Programmer K i s t l e r 504E Dual Mode Amplifiers K i s t l e r 201B4 Pressure Transducers Medtherm 64 Series Heat Flux Sensor (Schmidt-Boelter type) Systron Donner 8120 Time Code Generator Tektronix 184 Time Mark Generator Honeywell 117 Accudata Amplifiers Krohn-Hite 3202 Variable F i l t e r Honeywell 1858 CRT Visicorder w/1881, 1882 and 1883 Amplifiers ERA TR36-8M Power Supply Newport 60-3 Amplifier HyCam Model 41—0004 High Speed Movie Camera M i l l i k e n DSB-5A High Speed Movie Camera Polaroid SX-70 Camera Canon A - l Reflex Camera Support and C a l i b r a t i o n Equipment Cohu 335 DC Voltage Standard Dana 5600 D i g i t a l Voltmeter B e l l & Howell TD 2903-4B Tape Degausser HP 5300A Measuring System HP 3311 Function Generator Beckman 905 WWV Receiver David Clark 10SB-A Sound Powered Head Sets 40 f t . Instrumentation T r a i l e r w/instailed equipment, racks, patch paneling, l i g h t i n g systems, heating system, and i s o l a t i o n transformer K i s t l e r 563 A Charge Calibrator Tektronix 561A Oscilloscope with 3A6 A m p l i f i e r and 3B4 Time Base Plug-Ins. Pressure Transducer Pulse C a l i b r a t i o n Systems


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Tests must be properly instrumented to meet the c r i t e r i a s p e c i f i e d e a r l i e r i n this chapter. A l l instrumentation should be selected to have the necessary response time and bandwidth equivalent to the anticipated overpressures and heat f l u x e s . Instrumentation must also be properly calibrated to ensure v a l i d i t y of the data.


B l a s t pressure gages, heat f l u x transducers, and sound l e v e l meters are to be located a t the probable head l o c a t i o n of the operator and a t representative positions where transient personnel may be located. Documentation of the tests should a l s o be provided by s t i l l photography, video camera/recorder systems, and high speed photography. The high speed photography with a minimum speed of 500 frames per second i s necessary to be able to see any flame front e x i t i n g a s h i e l d . A l i s t of t y p i c a l instrumentation used on an operational s h i e l d test i s shown on Table I I , (see reference 4). INDUSTRIAL SAFETY PROVISIONS. In the design of the APE and associated operational s h i e l d , conventional machine design practices are used to protect operators from hazards associated with moving parts. Proper techniques f o r guarding of hazardous machine areas are used, including the use of i n t e r l o c k s i n the control system to prevent movements u n t i l c e r t a i n conditions are s a t i s f i e d , or to stop movements i n emergency s i t u a t i o n s SUMMARY. The safety record associated with the use of APE operated remotely or w i t h i n operational shields i s excellent. Operational shields that are properly designed, fabricated, and tested do provide operators with adequate protection, and ensures t h e i r safety during hazardous operations.

Literature Cited 1. Mil-STD 398; Shields, Operational for Ammunition Operations, Criteria for Design of and Test for Acceptance; 5 November 1976. 2. "Explosives in Enclosed Spaces", U.S. Naval Ordnance Laboratory NavOrd Reports 2934 and 3890; Sixth Symposium on Combustion, Reinhold Publishers, Inc. N.Y., 1957 p. 648 3. CPIA Publication 394, Hazards of Chemical Rockest and Propellants, Volume I, Safety, Health, and the Environment: September 1984, Healy, J., Weissman, S., Werner, H., and Dobbs, N. 4. Priming Fragment Characteristics and Impact Effects on Protective Barriers, Picatinny Arsenal, Dover, New Jersey, Technical Report 4903, December 1975. 5. Miller, J., APE 1011M6 Operational Shield Tests MK39 Primer in Empty 6 Inch/47 Cartridge Case (1340 Grains Black Powder), Ammunition Equipment Directorate, Tooele Army Depot, Tooele, Utah, D/AE Report 05-82, 22 February 1982. RECEIVED April 21, 1987


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